"Singing is what I do. I'm not a novice at it. I enjoy it. Just the fact that it's here in Pittsburgh, to see my son play and to get this opportunity, it's a once-in-a-lifetime opportunity and I'm glad they invited me," she told Channel 4 Action Sports' Justin Rose.

"It's always great to watch her go out and perform," said Andrew McCutchen. "Every day is always new and it's always great to be able to hear her just show her gift."

But it wasn't his mom's first time performing in front of a big league crowd. Last August, she sang before a Pirates-Diamondbacks game.

"They asked me back. It came to fruition, I think, maybe Andrew or someone had heard me sing and mentioned it to (team president) Frank Coonelly. One thing led to another and I got invited. I think my audition was down in Bradenton to see if I really could sing and it kind of took off from there. I'm fortunate they liked what they heard and invited me back," Petrina McCutchen said.

But what about her son? Can "Cutch" carry a tune?

"Andrew can sing. He used to sing at church. He did pretty good when he sang, so he can sing, but he just doesn't. But he can," she said.